Official Cummins QSC-500 Thread

Airplane Guy said:
I have a 2006 44, on the last trip of the season , and continuing this season, I've noticed a fuel flow split starting at 2150 rpm. Port engine 14.8, Stb 12.1. No smoke from the port engine. The load was also split , at 79%, Port 62%, Stb 47%. the boat tracks straight, and after a 4 hour run and topping the tanks, both were within 2 gallons of each other. I believe I have an indication problem( I hope) and was told that the engine load uses a calculation of fuel flow. Does anyone know where the fuel flow transducers are and if they can be swapped?
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Problem finally solved , the mechanic that serviced the engines prior to my last trip, turned off the starboard fuel return valve on top of the tank for some unknown reason. It was discovered after the fuel flow magically returned to normal for the last 10 minutes of a trip to Point Judith, making me temporarily happy until after topping off the fuel only to find 10 gallons (at least) under my engine from the ruptured fuel return line. Replaced line, opened valve, fired mechanic ,fuel flows normal
 
swaterhouse said:
Have either fuel/gear cooler or heat exchanger ever been done? The fuel cooler is already more than half off to get at the after cooler, and if its been more than 5 years your due for a coolant flush anyway so its not that much more work to pull them off.

That said, I am 99% sure I was the first to do mine after 9 years and they weren't all that bad so barnacle buster may be fine for the fuel cooler and heat exchanger.

As you discovered pulling apart the aftercooler is very important!
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Maintenance records on this one are a little sketchy unfortunately, so I can't say for sure what's been done to the fuel/oil cooler or HX. During the aftercooler cleaning we did borescope the HX, and it was pretty grody, but I've seen a lot worse. I'm going to do a little more digging re:Barnacle Buster before I pull the trigger on a full R&R on the coolers and HX.
 
Have about 1,000 hours on engines. I am the new owner and got boat with 950 hours. I put new serpentine belts on last Fall and ran boat maybe 15 hours after. I was in bilge Saturday and observed what looks like soot on stbd engine only. See pics. Engines are not running hot. One suggestion I received was that it was belt dust. What are your thoughts? Thanks -
IMG_6166.JPG

IMG_6167.JPG
 
It does look like belt dust. The same belt dust condition was noted during my pre-purchase survey, the surveyor stated that it would be beyond his scope to remove the belt cover during a survey but did offer a few suggestions about what the cause might be. The list included old belt getting worn, a worn alternator or idler pulley bearing causing excessive drag and the self adjusting idler pulley sticking were top suspects. After buying the boat and having my mechanic look into it, he found that the belt had been installed incorrectly, the belt was routed over the top center pulley but should have been routed under the pulley. Routing over the pulley caused the belt to come in contact with the metal bar that the cover attaches to. The cover mounting was carving a groove in the belt.
IMG_5191.jpg
 
Does look like belt dust. I had the same appearance when mine was purchased. Cummins guy told me to change it first chance. Did that and it went away.

Bennett
 
When I first bought my last boat I replaced both belts. My mechanic asked why I wanted to do that, I replied look at the dust. He said new belts would put out dust soon after install. I said do it anyway. Sure enough in 10 or so hours dust started to reappear. Maybe nothing to worry about.
 
Airplane Guy said:
Problem finally solved , the mechanic that serviced the engines prior to my last trip, turned off the starboard fuel return valve on top of the tank for some unknown reason. It was discovered after the fuel flow magically returned to normal for the last 10 minutes of a trip to Point Judith, making me temporarily happy until after topping off the fuel only to find 10 gallons (at least) under my engine from the ruptured fuel return line. Replaced line, opened valve, fired mechanic ,fuel flows normal
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Just returned from maiden voyage with 2006 44DA QSC 500's purchased last fall. During the winter, had all maintenance performed (aftercoolers, heat xchangers, etc.) to bring engines in line with Cummins requirements. All readings seemed fine except GPH burn. Stbd reading was approx 3-4 GPH higher than Port during most of the trip. I have researched and read many of the posts on this thread which are quite helpful. I am only speculating, but could the issue be a faulty sensor? If this could be indicative of something else, then I will promptly arrange for visit from local engine tech. The boat ran fine otherwise. Thanks. Frank C.
 
Sindbad said:
Just returned from maiden voyage with 2006 44DA QSC 500's purchased last fall. During the winter, had all maintenance performed (aftercoolers, heat xchangers, etc.) to bring engines in line with Cummins requirements. All readings seemed fine except GPH burn. Stbd reading was approx 3-4 GPH higher than Port during most of the trip. I have researched and read many of the posts on this thread which are quite helpful. I am only speculating, but could the issue be a faulty sensor? If this could be indicative of something else, then I will promptly arrange for visit from local engine tech. The boat ran fine otherwise. Thanks. Frank C.
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Any black smoke?

Were the temps and boost numbers the same on both engines - these are both indications of how much load the engine is experiencing?

Did you try a WOT run for a minute to see if both engines spin up to 2650+ RPMS?
 
swaterhouse said:
Any black smoke?

Were the temps and boost numbers the same on both engines - these are both indications of how much load the engine is experiencing?

Did you try a WOT run for a minute to see if both engines spin up to 2650+ RPMS?
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Temps and boost numbers were essentially the same. WOT run showed both engines at 2650 rpm's.
 
Sindbad said:
Just returned from maiden voyage with 2006 44DA QSC 500's purchased last fall. During the winter, had all maintenance performed (aftercoolers, heat xchangers, etc.) to bring engines in line with Cummins requirements. All readings seemed fine except GPH burn. Stbd reading was approx 3-4 GPH higher than Port during most of the trip. I have researched and read many of the posts on this thread which are quite helpful. I am only speculating, but could the issue be a faulty sensor? If this could be indicative of something else, then I will promptly arrange for visit from local engine tech. The boat ran fine otherwise. Thanks. Frank C.
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Frank, make sure both fuel return valves are open, one of mine was closed after a major service, your engine loads with that fuel flow difference should be also split, if they are even ,then you may just have an indication issue.
 
Airplane Guy said:
Frank, make sure both fuel return valves are open, one of mine was closed after a major service, your engine loads with that fuel flow difference should be also split, if they are even ,then you may just have an indication issue.
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Where are the return valves located?
 
Sindbad said:
Where are the return valves located?
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The port is on top of the tank, you cant see them, you need to do it by feel. I open the hatch over the generator and lay down on the closed main engine hatch, one valve is fairly close to the corner closest to you at that point, the other one is just to port of that. Not easy to feel/reach in but they are there! The handles are parallel with the hose to open, perpendicular to close.

The starboard valves are mounted to the "ceiling" just above the racor filter.
 
swaterhouse said:
The port is on top of the tank, you cant see them, you need to do it by feel. I open the hatch over the generator and lay down on the closed main engine hatch, one valve is fairly close to the corner closest to you at that point, the other one is just to port of that. Not easy to feel/reach in but they are there! The handles are parallel with the hose to open, perpendicular to close.

The starboard valves are mounted to the "ceiling" just above the racor filter.
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Thanks swaterhouse.
 
I always thought the yellow handle valves levers were to shut off fuel flow to the racors. So I was wondering why I noticed 4 of them when I only have 3 engines (2 mains and genny)
 
Sindbad said:
Just returned from maiden voyage with 2006 44DA QSC 500's purchased last fall. During the winter, had all maintenance performed (aftercoolers, heat xchangers, etc.) to bring engines in line with Cummins requirements. All readings seemed fine except GPH burn. Stbd reading was approx 3-4 GPH higher than Port during most of the trip. I have researched and read many of the posts on this thread which are quite helpful. I am only speculating, but could the issue be a faulty sensor? If this could be indicative of something else, then I will promptly arrange for visit from local engine tech. The boat ran fine otherwise. Thanks. Frank C.
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Master Cummins guy told me loads on each will be different due to driveline (props, bearings, trans, etc). How were the load numbers, and does it match percentage wise with your increased GPS numbers?
 
importmonkey said:
Master Cummins guy told me loads on each will be different due to driveline (props, bearings, trans, etc). How were the load numbers, and does it match percentage wise with your increased GPS numbers?
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Import Monkey - not sure yet. I spoke with local Cummins tech. He suggested taking some Boost readings over next few outings to see how they compare.
 
While doing a post-trip bilge check I noticed a slight smell of antifreeze and that the overflow reservoir on my starboard engine was a little low. Further inspection found a slight leak at the heat exchanger freeze plug. It looks like there are 4 on each exchanger and only 1 of the 8 are leaking. So, I have a few questions. What caused this to happen, regular wear and tear or is there a bigger problem looming? Is this a simple DIY repair as it looks to be? During the trip, both engines ran between 172-174 as they normally do.
 
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